Geometrically reconfigurable propellers

ABSTRACT

An aerial vehicle may be equipped with propellers having reconfigurable geometries. Such propellers may have blade tips or other features that may be adjusted or reconfigured while the aerial vehicle is operating, on any basis. Propellers having reconfigurable blade tips joined to blade roots may cause the blade tips to be aligned with the blade roots, or substantially perpendicular to the blade roots, e.g., in order to counter adverse effects of tip vortices, or at any intervening angle. The propellers may be reconfigured at predetermined times during operation of an aerial vehicle, or upon sensing one or more operational characteristics or environmental conditions, as may be desired or required.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/454,785, now U.S. Pat. No. 10,179,646, filed Mar. 9, 2017, which is acontinuation of U.S. patent application Ser. No. 14/975,167, now U.S.Pat. No. 9,592,910, filed Dec. 18, 2015. The contents of each of theseapplications are incorporated by reference herein in their entirety.

BACKGROUND

A wingtip vortex is a natural phenomenon that occurs due to pressuredifferences that form when a blade is subjected to fluid flow. Forexample, when an airfoil is provided at a positive angle, a pressuredifferential exists between an upper surface of the airfoil and a lowersurface of the airfoil. More specifically, a pressure above the airfoilis less than atmospheric pressure, while a pressure below the airfoilequals or exceeds atmospheric pressure. Because air will flow consistentwith a pressure gradient, e.g., from a high pressure region to a lowpressure region, and because a path of least resistance is located at ornear an airfoil's tips, air tends to flow outwardly in a spanwise mannertoward a blade tip, from a bottom of the airfoil, upwardly and aroundthe tip. In a fixed-wing aircraft, air flows outwardly from a fuselageto which a wing is mounted, toward a tip of the wing. In a rotating wingaircraft, air flows outwardly from a hub about which a propellerrotates, toward tips of the respective blades. Upon reaching the tips ofthe blades, the air flow spillage spirals beyond the tip of the bladeand forms a whirlpool that is known as a vortex.

Wingtip vortices induce substantial amounts of drag. For example, airthat spirals beyond a blade tip may combine with wash to form a rapidlyspinning trailing vortex. Wingtip vortices thereby decrease theefficiency of a blade, in view of the increased energy that must beexpended in order to overcome the drag induced thereby. Typically, theintensity of a wingtip vortex formed during flight is a function of anumber of variables, including but not limited to the weight or speed ofan aircraft, or an angle of one or more of its blades. Wingtip vorticesmay also create wind turbulence or other hazardous effects for otheraircraft that may be operating nearby.

In the 1970s, during the midst of energy crises that drove up fuelprices around the world, researchers at the National Aeronautics & SpaceAdministration (NASA) began experimenting with winglets, or vertical (ornearly vertical) extensions provided at the ends of wings provided onfixed-wing aircraft. NASA's research determined that the use of wingletscould increase the range of fixed-wing aircraft at standard speeds, andimprove the ratios of induced drag to induced lift for such aircraft byseveral percent, particularly where fixed winglets were provided asintegral parts of the airfoils of the fixed wings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A through 1C are views of aspects of one aerial vehicle having apropeller with geometrically reconfigurable blades in accordance withembodiments of the present disclosure.

FIG. 2 is a block diagram of one system for operating an aerial vehiclehaving a propeller with a geometrically reconfigurable blade inaccordance with embodiments of the present disclosure.

FIG. 3 is a flow chart of one process for operating an aerial vehiclehaving a propeller with a geometrically reconfigurable blade inaccordance with embodiments of the present disclosure.

FIGS. 4A through 4C are views of reconfigurable propellers in accordancewith embodiments of the present disclosure.

FIG. 5 is a flow chart of one process for operating an aerial vehiclehaving a propeller with a geometrically reconfigurable blade inaccordance with embodiments of the present disclosure.

FIG. 6 is a view of aspects of one aerial vehicle having a propellerwith a geometrically reconfigurable blade in accordance with embodimentsof the present disclosure.

FIG. 7 is a flow chart of one process for operating an aerial vehiclehaving a propeller with a geometrically reconfigurable blade inaccordance with embodiments of the present disclosure.

FIG. 8 is a view of aspects of one aerial vehicle having a propellerwith a geometrically reconfigurable blade in accordance with embodimentsof the present disclosure.

DETAILED DESCRIPTION

As is set forth in greater detail below, the present disclosure isdirected to reconfigurable blade tips on propellers. More specifically,the systems and methods disclosed herein are directed to operatingaerial vehicles with propellers having blade tips or other features thatmay change their respective geometric configurations either staticallyor dynamically during operation based on prevailing operatingcharacteristics or environmental conditions. In some embodiments,propellers having two or more blades may include tip portions that maybe configured to rotate to varying extents with respect to axes definedby such blades. For example, in some embodiments, a blade tip may berotated from a positive normal cant angle (e.g., ninety degreesvertically upward with respect to an axis of the blade root extendingradially outward from a hub) to a negative normal cant angle (e.g.,ninety degrees vertically downward with respect to the axis), or to anyintervening cant angle with respect to a blade root between suchpositions. Moreover, in some embodiments, the blade tips may bemaintained at fixed, predetermined cant angles with respect to axes ofthe blades throughout various revolutions of the blades. In otherembodiments, the blade tips may be maintained at cant angles that varybased on the angles of rotation of the respective blades. In still otherembodiments, cant angles of the blade tips may be adjusted based on anyoperating characteristics or environmental conditions, or in response toany changes in such characteristics or conditions, as needed. Byenabling a geometric configuration of a blade to be varied duringoperation, the adverse effects of wingtip vortices or other conditionsmay be minimized or eliminated, as desired.

Referring to FIGS. 1A through 1C, views of aspects of one aerial vehicle110 having propellers with geometrically reconfigurable blades inaccordance with embodiments of the present disclosure are shown. As isshown in FIG. 1A, the aerial vehicle 110 (e.g., an unmanned aerialvehicle, or UAV) includes a plurality of propellers 120 that areconfigured for rotation by respective motors 160 provided thereon. Eachof the propellers 120 includes a fixed blade 130 joined to a distal endof a blade root 135 and a fixed blade 140 joined to a distal end of ablade root 145. The blade root 135 and the blade root 145 are eachmounted at a proximal end thereof to a hub 150 joined (e.g., by a mastor shaft 152) to one of the motors 160. The hub 150 further includes amast opening for receiving a mast or a shaft (not shown) of atransmission associated with one of the motors 160.

The motors 160 may be any type or form of motor (e.g., electric,gasoline-powered or any other type of motor) capable of generatingsufficient rotational speeds of the corresponding propellers 120 liftthe aerial vehicle 110 and any engaged payload, and to aeriallytransport the engaged payload thereby. Each of the motors 160 may besimilar or identical to one another, and may feature similar oridentical features (e.g., power sources, numbers of poles, whether themotors are synchronous or asynchronous) or operating characteristics(e.g., angular velocities, torques, operating speeds or operatingdurations). Alternatively, two or more of the motors 160 may havedifferent features or operating characteristics, based on an extent towhich use of such motors or their corresponding propellers 120 isdesired or required. Each of such motors 160 may be operatedindividually or in tandem with one another, for any purpose. Forexample, two or more of the motors 160 and their correspondingpropellers 120 may be operated to provide both lift and thrust, whiletwo or more of the motors 160 and their corresponding propellers 120 maybe operated to provide either lift or thrust.

The fixed blade 130 further includes a blade tip 132 mounted to thedistal end of the blade root 135 at a hinged connection 134. The bladetip 132 is configured to rotate about a tangential axis defined by thehinged connection 134 with respect to a radial axis defined by the bladeroot 135. The fixed blade 140 further includes a blade tip 142 mountedto the distal end of the blade root 145 at a hinged connection 144. Theblade tip 142 is configured to rotate about a tangential axis defined bythe hinged connection 144 with respect to a radial axis defined by theblade root 145. As is further shown in FIG. 1A, at time t₁, each of theblade tips 132, 142 is aligned along the radial axes defined by arespective one of the blade roots 135, 145.

Each of the blade tips 132, 142 and each of the blade roots 135, 145defines an airfoil shape for generating lift when the propeller 120 isrotated about an axis defined by the hub 150 and/or the motor 160, andmay, in some embodiments, include rounded leading edges and pointedtrailing edges that may include upper surfaces or lower surfaces havingsymmetrical or asymmetrical shapes or cross-sectional areas. The airfoilshapes defined by the blades 130, 140, and the angles at which the bladeroots 135, 145 are mounted to the hub 150, may be selected based on anamount of lift desired to be provided by the propeller 120.

In accordance with the present disclosure, propellers may be configuredwith blades having blade tips that may rotate with respect to axesdefined by such blades, e.g., the blade roots of the respective blades,either statically or dynamically during operation. As is shown in FIG.1B, the blade tip 132 is rotated vertically upward to a first cant angleθ1 with respect to the blade root 135, and the blade tip 142 is rotatedvertically upward to a second cant angle θ2 with respect to the bladeroot 145. The cant angles θ1, 02 are limited only by the constraintsresulting from the construction of the blades 130, 140.

The blade tips 132, 142 may be rotated with respect to the blade roots135, 145 at any time or in accordance with a predetermined schedule(e.g., based at least in part on a transit plan involving travel from anorigin to a destination, and optionally through one or more interveningwaypoints), or in response to a sensed operating characteristic (e.g.,dynamic attributes such as altitudes, courses, speeds, rates of climb ordescent, turn rates, accelerations, tracked positions, fuel level,battery level or radiated noise; or physical attributes such asdimensions of structures or frames, numbers of propellers or motors,operating speeds of such motors) or environmental condition (e.g.,temperatures, pressures, humidities, wind speeds, wind directions, timesof day or days of a week, month or year when an aerial vehicle isoperating, measures of cloud coverage, sunshine, or surface conditionsor textures).

Additionally, the blade tips 132, 142 may be rotated in any manner or byany means with respect to orientations or configurations defined by theblade roots 135, 145, and to any extent. For example, one or more of theblade roots 135, 145 may include one or more mechanical operators withinairfoils of the blade roots 135, 145 that are configured to cause theblade tips 132, 142 to be positioned at a selected cant angle withrespect to the blade roots 135, 145. As is shown in FIG. 1B, the bladeroot 135 may include a gear and cam assembly 136 that rotates based onthe rotation of the shaft 152, and causes a follower or push rod 138 tocause the blade tip 132 to be rotated about the hinge 134 to a differentcant angle accordingly. As is also shown in FIG. 1B, the blade root 145may include a cable-driven tension assembly 146 that causes a cable 148connected to the blade tip 142 to extend or retract against centrifugalforces acting on the blade tip 142, as necessary, in order to cause theblade tip 142 to be rotated about the hinge 144 to a different cantangle accordingly. Those of ordinary skill in the pertinent arts willrecognize that the blades 130, 140 may include any other mechanicaland/or electrical systems or operators (e.g., within the airfoils of theblade roots 135, 145) for changing the cant angles θ₁, θ₂ of the bladetips 132, 142 with respect to the blade roots 135, 145, or for otherwisegeometrically reconfiguring a propeller in accordance with the presentdisclosure.

The various components of the propeller 120 may be formed from anysuitable materials that may be selected based on an amount of lift thatmay be desired in accordance with the present disclosure. In someimplementations, aspects of the propeller 120 (e.g., the blade tips 132,142, the blade roots 135, 145 and/or the hub 150) may be formed from oneor more plastics (e.g., thermosetting plastics such as epoxy or phenolicresins, polyurethanes or polyesters, as well as polyethylenes,polypropylenes or polyvinyl chlorides), wood (e.g., woods withsufficient strength properties such as ash), metals (e.g., lightweightmetals such as aluminum, or metals of heavier weights including alloysof steel), composites or any other combinations of materials. In someimplementations, the aspects of the propeller 120 may be formed of oneor more lightweight materials including but not limited to carbon fiber,graphite, machined aluminum, titanium, or fiberglass.

Furthermore, in some embodiments, the various components of thepropeller 120 of FIG. 1A may be formed by modifying a standard propellerof any type, size, shape or form. For example, each of the blade tips132, 142 may be severed from a single blade of a multi-blade propeller,leaving behind the blade roots 135, 145, and reattached to the remainingblade roots 135, 145 from which the blade tips 132, 142 were cut by wayof the hinges 134, 144, which may be pivotable connections or shaftassemblies that may be installed between the blade roots 135, 145 andthe blade tips 132, 142. In some embodiments, the blade tips 132, 142may alternatively be provided with one or more biasing elements forurging the blade tips 132, 142 into a predetermined cant angle withrespect to a corresponding one of the blade roots 135, 145.

Additionally, the blade tips 132, 142, and/or the blade roots 135, 145may be solid or substantially solid, and formed from one or morehomogenous or heterogeneous materials. Alternatively, the blade tips132, 142 and/or the blade roots 135, 145 may be substantially hollow,e.g., each having a solid skin defining an airfoil having a hollowcavity therein, with one or more internal supports or structuralfeatures for maintaining a shape of the respective airfoils. Forexample, the propeller 120 or portions thereof may be formed fromdurable frames of stainless steel, carbon fibers, or other similarlylightweight, rigid materials and reinforced with radially aligned fibertubes or struts. Utilizing a propeller 120 having a substantially hollowcross-section thereby reduces the mass of the propeller 120, and enableswiring, cables and mechanical or electrical operators, e.g., one or morecomponents of the gear and cam assembly 136 and/or follower or push rod138 of the blade 130 or one or more components of the tension assembly146 and/or the cable 148 of the blade 140 to be passed therethrough, andin communication with one or more other control systems components orfeatures. Some other mechanical or electrical operators that may beutilized in accordance with the present disclosure include, but are notlimited to, gear boxes, worm gears, servo-controlled arms. For example,mechanical or electrical equipment that is similar to equipmentordinarily utilized to change angles of control surfaces such as flaps,rudders, or ailerons may be incorporated into the blade roots 135, 145and utilized to change the cant. The propeller 120 or such portionsthereof may further be filled with foam or other fillers, strengthenedwith walls or other supports, and covered with flexible skins forresisting moisture, erosion or any other adverse effects of theelements.

As is shown in FIG. 1C, the aerial vehicle 110 is operating with theblade tips 132, 142 of the propellers 120 at the cant angles θ₁, θ₂ withrespect to the corresponding blade roots 135, 145 at time t₂.

Accordingly, the systems and methods of the present disclosure aredirected to aerial vehicles having rotating propellers with blade tipsor other features that may be geometrically modified in flight. A bladetip or other feature may be repositioned to various cant angles withrespect to a blade root or other components of a propeller either on astatic basis, e.g., where the propeller is rotated with the blade tipsat fixed cant angles, or on a dynamic basis, e.g., where the cant anglesof such blade tips change on a regular or irregular basis during flight.Additionally, the blade tips may be repositioned based on actual orpredicted operating characteristics, actual or predicted environmentalconditions, or any other factor. The blade tips may be repositioned byany mechanical or electrical system, which may be provided within acavity defined within a hollow or substantially hollow airfoil, and toany degree or extent with respect the blade roots to which such tips arejoined.

A wingtip vortex is a circular pattern of rotating air that follows anairfoil as lift is generated. High pressure on a lower surface of anairfoil and low pressure on an upper surface of the airflow results inan airflow that curls upwardly around a tip of the airfoil, in aspiraling fashion. In a fixed-wing aircraft, a wingtip vortex followsthe tips of each of the wings, as a result of spanwise variation in thelift generated by the wings. In a rotating wing aircraft, however, eachof the wingtip vortices departing from a rotating propeller follows ahelical path. A wingtip vortex results in substantial amounts of induceddrag and imparts downwash from the downwardly spiraling vortices fromeach of the wings. Accordingly, wingtip vortices are primarycontributors to wake turbulence. For example, in a fixed-wing aircraft,wingtip vortices generated from each of the wings spiral in oppositerotational directions and never merge. Instead, the vortices may lingerbehind the aircraft and dissipate over time.

To address the adverse effects of wingtip vortices, extensions known aswinglets have been installed at tips of wings of fixed-wing aircraft,such as jumbo jets or other airplanes. A winglet is an angled or curvedextensions of a wing tip provided at a vertical or nearly verticalupward angle, or cant angle, with respect to a blade root. In thepresence of airflow resulting from a pressure differential existingbetween upper and lower surfaces of a blade, a winglet provided at awingtip results in a horizontal lift component that can smooth airflowexisting at the wingtip, and reduce induced drag. As a vortex thatbegins to rotate from below a wing contacts an angled surface of awinglet, forces of thrust and additional lift are generated. A wingletmay be provided as separate or discrete components joined to a bladeroot in an angled or curved manner, or may be integral extensions of theblade root. Winglets also typically include spanwise cross-sectionalareas of decreasing size, and are typically provided as trapezoidal orellipsoidal extensions from similarly shaped blade roots at varyingpositive angles (e.g., cant angles) with respect to the blade roots.

The use of winglets tends to change the operational characteristics ofan aircraft, however. For example, a winglet may cause an aircraft to besubject to increased lateral forces during evolutions such as landingsor takeoffs, and may require the aircraft to be handled differentlydepending on prevailing weather conditions. The benefits of a wingletmay vary as functions of speed, altitude or a number of other factors.Heretofore, winglets have been provided in fixed orientations orconstructions with respect to cant angles of blade roots, e.g., atangles that do not and cannot change, and are typically utilized only infixed-wing aircraft.

The systems and methods of the present disclosure are directed topropeller blades having reconfigurable geometric features, including butnot limited to blade tips provided at mechanically adjustable cantangles with respect to their blade roots. The blade tips may be discretecomponents joined to the blade roots by hinges or other like featuresor, alternatively, the blade tips may be adjustable portions of bladesthat are integrally formed as a single unit, e.g., within a common skinof the blade root. The blade tips may be repositioned to any relativecant angle with respect to axes defined by blade roots to which suchtips are joined. Moreover, the blade tips may be repositioned using anymechanical or electrical systems, including one or more cam or gearassemblies, motors, electromagnetic systems or tensioning members thatcause the blade tips to be drawn radially inward toward a hub of apropeller, in opposition to one or more centrifugal forces acting uponthe propeller. Such systems may further incorporate one or moremechanical stops for preventing blade tips from rotating beyond apredetermined limit (including but not limited to ninety degrees, or90°, or zero degrees, or 0°) into the blade tips or blade roots, or oneor more biasing elements, such as torsion springs, for biasing the bladetips into one or more predetermined orientations with respect to theblade roots.

In some embodiments of the present disclosure, a blade tip of areconfigurable propeller may be realigned to a fixed cant angle withrespect to a blade root to which the blade tip is joined, e.g., in astatic manner. For example, when a reconfigurable propeller provided onan operating aerial vehicle includes at least one blade tip provided ata first cant angle with respect to a blade root to which the blade tipis joined, and the operation of the aerial vehicle would be enhancedwith a blade tip at a second cant angle, the blade tip may be realignedfrom the first cant angle to the second cant angle in response to acontrol signal, or based on a sensed environmental condition oroperational characteristic, including but not limited to information ordata regarding acoustic conditions within a vicinity of the aerialvehicle, or acoustic energies radiating from the aerial vehicle. Theblade tips may be repositioned, as necessary, depending on an operatingmode of an aerial vehicle, or based on any other criteria. For example,an aerial vehicle equipped with a geometrically configurable propellerin accordance with embodiments of the present disclosure may cause thepropeller to operate with blade tips oriented at substantially verticalcant angles with respect to blade roots to which such tips are joinedduring take-offs and landings (e.g., perpendicular to the blade roots),and with the blade tips co-aligned with the blade roots duringhorizontal flight in order to reduce drag, thereby enabling the samepropeller to operate in an optimal manner in different modes ofoperation of the aerial vehicle.

In some other embodiments of the present disclosure, a blade tip of areconfigurable propeller may be realigned in a dynamic manner, such thatthe blade tip is provided at varying cant angles with respect to axesdefined by the blade root to which the blade tip is joined duringoperation. Dynamic variations of cant angles may be distinguished fromstatic variations of such angles based on the intervals for which bladetips remain fixed at an given cant angle, with statically varying bladetips remaining at such angles for longer durations, and dynamicallyvarying blade tips remaining at such angles for shorter durations. Insome embodiments, the cant angle of the blade tip may be changed on acyclic basis, e.g., such that the cant angle of the blade tip withrespect to an axis defined by an extension of the blade root from thehub is determined based on an angular orientation of the blade about anaxis of rotation defined by a mast or shaft of a motor or other primemover. In this regard, the orientation of the blade tip or,alternatively, a length of a blade, may be varied as the propellerrotates about the axis of rotation. In some embodiments, areconfigurable propeller may substantially co-align blade tips withblade roots to which the blade tips are joined when the propeller isaligned in a direction of travel, e.g., in a longitudinal orientation,to minimize induced drag in forward flight, and may align the blade tipsvertically or nearly vertically upward, or substantially perpendicularto such roots, when the propeller is aligned perpendicular to thedirection of travel, e.g., in a transverse orientation. Thus, thereconfigurable propeller may take advantage of the benefits associatedwith wingtips on a rotating blade while also reducing levels of dragthat would otherwise be generated by such blade tips during forwardflight.

In still other embodiments of the present disclosure, a blade tip of areconfigurable propeller may be realigned in a dynamic manner subject tofeedback provided by one or more sensors. For example, where an aerialvehicle operating one or more reconfigurable propellers having bladetips that are oriented vertically or nearly vertically senses crosswinds or other conditions that may be exacerbated based on the cantangles of such tips, the aerial vehicle may cause the cant angles ofsuch tips to be reduced accordingly. Conversely, where an aerial vehicleis determined to be radiating noise at a certain sound pressure level orfrequency in excess of one or more standing or temporary limits, apropeller may be reconfigured accordingly. Any type or form of sensor orcontrol system may be used to identify an environmental condition oroperational characteristic that requires a reconfiguration of apropeller, e.g., a change in a cant angle of a blade tip with respect toa blade root, and the propeller may be reconfigured accordingly.

The extent to which cant angles of blade tips provided on a propellerblade are dynamically varied, and the periodicity with which such anglesare so varied, may be determined based on any number of relevantfactors. In some embodiments, an extent to which cant angles of suchtips are varied, or the periodicity with which the cant angles arevaried, may be determined with linear proportionality to one or moresensed conditions. For example, where an attribute or factor indicativeof an operational characteristic of the aerial vehicle or anenvironmental condition within a vicinity of the aerial vehicle is at afirst value, a blade tip may be aligned at a first cant angle that islinearly proportional to the first value, or may be varied at a firstperiodicity that is linearly proportional to the first value. Where theattribute or factor indicative of the operational characteristic or theenvironmental condition changes to a second value, the blade tip may bechanged to a second cant angle that is linearly proportional to thesecond value, or may be varied at a second periodicity that is linearlyproportional to the second value. In some other embodiments, the extentto which cant angles of blade tips are varied, or the periodicity withwhich the cant angles are varied, may be determined according to a jumpfunction, e.g., immediately in response to a change in a sensedcondition or by a predetermined extent, or in a smoothed manner, or withhysteresis. Any basis for determining an extent to which a cant angle ofa blade tip may be varied, or the periodicity with which the cant anglemay be varied, may be utilized in accordance with the presentdisclosure.

Moreover, those of ordinary skill in the pertinent arts will recognizethat the systems and methods of the present disclosure may be utilizedto realign or readjust any attribute of a reconfigurable propeller,including not only cant angles of blade tips with respect to bladeroots, but also blade pitches, blade lengths, blade rake angles, or anyother attribute of the propeller. Furthermore, those of ordinary skillin the pertinent arts will further recognize that an aerial vehicle maybe equipped with reconfigurable propellers in a homogenous manner, e.g.,such that each of the blades of each of the propellers includes commonfeatures for reconfiguring such blades, for example, by adjusting cantangles of blade tips with respect to blade roots in an identicalfashion. Alternatively, an aerial vehicle may be equipped with somereconfigurable propellers and some propellers that are notreconfigurable, and a reconfigurable propeller may include differentfeatures for reconfiguring different blades provided on the propeller indifferent manners. Likewise, a propeller may be reconfigured based onnot only sensed environmental conditions or operational characteristics(e.g., actual conditions or characteristics) but also predictedenvironmental conditions or operational characteristics, or on any otherfactors.

Referring to FIG. 2, a block diagram of components of one system 200 foroperating an aerial vehicle having a propeller with reconfigurable bladetips in accordance with embodiments of the present disclosure is shown.The system 200 of FIG. 2 includes an aerial vehicle 210 and a dataprocessing system 270 connected to one another over a network 280.

The aerial vehicle 210 includes a processor 212, a memory 214 and atransceiver 216, as well as a plurality of environmental or operationalsensors 220, a plurality of sound sensors 230 and a plurality of bladecontrollers 240.

The processor 212 may be configured to perform any type or form ofcomputing function associated with the operation of the aerial vehicle210, including but not limited to the execution of one or more machinelearning algorithms or techniques, e.g., for predicting one or moreattributes of the aerial vehicle 210 based on historical data regardingprior operations of the aerial vehicle 210, or one or more other aerialvehicles. The processor 212 may control any aspects of the operation ofthe aerial vehicle 210 and the one or more computer-based componentsthereon, including but not limited to the transceiver 216, theenvironmental or operational sensors 220, the sound sensors 230, and/orthe blade controllers 240. The aerial vehicle 210 may likewise includeone or more control systems (not shown) that may generate instructionsfor operating any number of components of the aerial vehicle 210, e.g.,one or more rotors, motors, rudders, ailerons, flaps or other componentsprovided thereon. Such control systems may be associated with one ormore other computing devices or machines, and may communicate with thedata processing system 270 or one or more other computer devices (notshown) over the network 280, through the sending and receiving ofdigital data. The aerial vehicle 210 further includes one or more memoryor storage components 214 for storing any type of information or data,e.g., instructions for operating the aerial vehicle, or information ordata captured by one or more of the environmental or operational sensors220, the sound sensors 230, and/or the blade controllers 240.

The transceiver 216 may be configured to enable the aerial vehicle 210to communicate through one or more wired or wireless means, e.g., wiredtechnologies such as Universal Serial Bus (or “USB”) or fiber opticcable, or standard wireless protocols such as Bluetooth® or any WirelessFidelity (or “WiFi”) protocol, such as over the network 280 or directly.

The environmental or operational sensors 220 may include any componentsor features for determining one or more attributes of an environment inwhich the aerial vehicle 210 is operating or may be expected to operate,or an operational characteristic of the aerial vehicle 210, includingextrinsic information or data or intrinsic information or data. As isshown in FIG. 2, the environmental or operational sensors 220 mayinclude, but are not limited to, a Global Positioning System (“GPS”)receiver or sensor 221, a compass 222, a speedometer 223, an altimeter224, a thermometer 225, a barometer 226, a hygrometer 227, or agyroscope 228. The GPS sensor 221 may be any device, component, systemor instrument adapted to receive signals (e.g., trilateration data orinformation) relating to a position of the handheld device 250 from oneor more GPS satellites of a GPS network (not shown). The compass 222 maybe any device, component, system, or instrument adapted to determine oneor more directions with respect to a frame of reference that is fixedwith respect to the surface of the Earth (e.g., a pole thereof). Thespeedometer 223 may be any device, component, system, or instrument fordetermining a speed or velocity of the aerial vehicle 210, and mayinclude related components (not shown) such as pitot tubes,accelerometers, or other features for determining speeds, velocities, oraccelerations.

The altimeter 224 may be any device, component, system, or instrumentfor determining an altitude of the aerial vehicle 210, and may includeany number of barometers, transmitters, receivers, range finders (e.g.,laser or radar) or other features. The thermometer 225, the barometer226 and the hygrometer 227 may be any devices, components, systems, orinstruments for determining local air temperatures, atmosphericpressures, or humidities, respectively, within a vicinity of the aerialvehicle 210. The gyroscope 228 may be any mechanical or electricaldevice, component, system, or instrument for determining an orientation,e.g., the orientation of the aerial vehicle 210. For example, thegyroscope 228 may be a traditional mechanical gyroscope having at leasta pair of gimbals and a flywheel or rotor. Alternatively, the gyroscope228 may be an electrical component such a dynamically tuned gyroscope, afiber optic gyroscope, a hemispherical resonator gyroscope, a Londonmoment gyroscope, a microelectromechanical sensor gyroscope, a ringlaser gyroscope, or a vibrating structure gyroscope, or any other typeor form of electrical component for determining an orientation of theaerial vehicle 210.

Those of ordinary skill in the pertinent arts will recognize that theenvironmental or operational sensors 220 may include any type or form ofdevice or component for determining an environmental condition within avicinity of the aerial vehicle 210, or an operational characteristic ofthe aerial vehicle 210, in accordance with the present disclosure. Forexample, the environmental or operational sensors 220 may include one ormore air monitoring sensors (e.g., oxygen, ozone, hydrogen, carbonmonoxide or carbon dioxide sensors), infrared sensors, ozone monitors,pH sensors, magnetic anomaly detectors, metal detectors, radiationsensors (e.g., Geiger counters, neutron detectors, alpha detectors),attitude indicators, depth gauges, accelerometers, tachometers or thelike, as well as one or more imaging devices (e.g., digital cameras),and are not limited to the sensors 221, 222, 223, 224, 225, 226, 227,228 shown in FIG. 2.

The sound sensors 230 may include other components or features fordetecting and capturing sound energy in a vicinity of an environment inwhich the aerial vehicle 210 is operating, or may be expected tooperate. As is shown in FIG. 2, the sound sensors 230 may include amicrophone 232, a piezoelectric sensor 234, and a vibration sensor 236.The microphone 232 may be any type or form of transducer (e.g., adynamic microphone, a condenser microphone, a ribbon microphone, acrystal microphone) configured to convert acoustic energy of anyintensity and across any or all frequencies into one or more electricalsignals, and may include any number of diaphragms, magnets, coils,plates, or other like features for detecting and recording such energy.The microphone 232 may also be provided as a discrete component, or incombination with one or more other components, e.g., an imaging devicesuch as a digital camera. Furthermore, the microphone 232 may beconfigured to detect and record acoustic energy from any and alldirections.

The piezoelectric sensor 234 may be configured to convert changes inpressure, including but not limited to such pressure changes that areinitiated by the presence of acoustic energy across various bands offrequencies, to electrical signals, and may include one or morecrystals, electrodes or other features. The vibration sensor 236 may beany device configured to detect vibrations of one or more components ofthe aerial vehicle 210, and may also be a piezoelectric device. Forexample, the vibration sensor 236 may include one or moreaccelerometers, e.g., an application-specific integrated circuit and oneor more microelectromechanical sensors in a land grid array package,that are configured to sense differential accelerations along one ormore axes over predetermined periods of time and to associate suchaccelerations with levels of vibration and, therefore, sound.

The blade controllers 240 may include a plurality of components foroperating and/or adjusting one or more attributes of one of a pluralityof reconfigurable blades 242-1 . . . 242-n, e.g., at a predeterminedtime or in accordance with a predefined schedule, or in response to oneor more control signals, sensed environmental conditions or sensedoperational characteristics. For example, such controllers 240 may beconfigured to rotate blade tips of such reconfigurable blades 242-1 . .. 242-n about axes defined with respect to blade roots to which suchblade tips are joined. Alternatively, the blade controllers 240 may beconfigured to change any number of other attributes of suchreconfigurable blades 242-1 . . . 242-n. The blade controllers 240 maythus control, initiate or operate one or more mechanical or electricalfeatures provided on or in association with such reconfigurable blades242-1 . . . 242-n for altering one or more attributes thereof.

The data processing system 270 includes one or more physical computerservers 272 having a plurality of data stores (e.g., data bases) 276associated therewith, as well as one or more computer processors 274provided for any specific or general purpose. For example, the dataprocessing system 270 of FIG. 2 may be independently provided for theexclusive purpose of receiving, analyzing, or storing informationregarding one or more missions or evolutions that have been performed orare scheduled to be performed by the aerial vehicle 210. Alternatively,the data processing system 270 may be provided in connection with one ormore physical or virtual services configured to receive, analyze, orstore instructions for operating the aerial vehicle 210 or otherinformation or data, as well as to perform one or more other functions.The servers 272 may be connected to or otherwise communicate with thedata stores 276 and the processors 274. The data stores 276 may storeany type of information or data, including but not limited toinformation or data regarding the operation of the aerial vehicle 210,e.g., with respect to one or more attributes of the reconfigurableblades 242-1 . . . 242-n, or information or data regarding environmentalconditions, operational characteristics, or positions, for any purpose.

The servers 272 and/or the computer processors 274 may also connect toor otherwise communicate with the network 280, as indicated by line 278,through the sending and receiving of digital data. For example, the dataprocessing system 270 may include any facilities, stations or locationshaving the ability or capacity to receive and store information or data,such as media files, in one or more data stores, e.g., media filesreceived from the aerial vehicle 210, or from one another, or from oneor more other external computer systems (not shown) via the network 280.In some embodiments, the data processing system 270 may be provided in aphysical location. In other such embodiments, the data processing system270 may be provided in one or more alternate or virtual locations, e.g.,in a “cloud”-based environment. In still other embodiments, the dataprocessing system 270 may be provided onboard one or more aerialvehicles, including but not limited to the aerial vehicle 210.

The network 280 may be any wired network, wireless network, orcombination thereof, and may comprise the Internet in whole or in part.In addition, the network 280 may be a personal area network, local areanetwork, wide area network, cable network, satellite network, cellulartelephone network, or combination thereof. The network 280 may also be apublicly accessible network of linked networks, possibly operated byvarious distinct parties, such as the Internet. In some embodiments, thenetwork 280 may be a private or semi-private network, such as acorporate or university intranet. The network 280 may include one ormore wireless networks, such as a Global System for MobileCommunications (GSM) network, a Code Division Multiple Access (CDMA)network, a Long Term Evolution (LTE) network, or some other type ofwireless network. Protocols and components for communicating via thenetwork 280 and/or the Internet or any of the other aforementioned typesof communication networks are well known to those skilled in the art ofcomputer communications and thus, need not be described in more detailherein.

The computers, servers, devices and the like described herein have thenecessary electronics, software, memory, storage, databases, firmware,logic/state machines, microprocessors, communication links, displays orother visual or audio user interfaces, printing devices, and any otherinput/output interfaces to provide any of the functions or servicesdescribed herein and/or achieve the results described herein. Also,those of ordinary skill in the pertinent art will recognize that usersof such computers, servers, devices and the like may operate a keyboard,keypad, mouse, stylus, touch screen, or other device (not shown) ormethod to interact with the computers, servers, devices and the like, orto “select” an item, link, node, hub or any other aspect of the presentdisclosure.

The aerial vehicle 210 or the data processing system 270 may use anyweb-enabled or Internet applications or features, or any otherclient-server applications or features including E-mail or othermessaging techniques, to connect to the network 280, or to communicatewith one another, such as through short or multimedia messaging service(SMS or MMS) text messages. For example, the aerial vehicle 210 may beadapted to transmit information or data in the form of synchronous orasynchronous messages to the data processing system 270 or to any othercomputer device in real time or in near-real time, or in one or moreoffline processes, via the network 280. Those of ordinary skill in thepertinent art would recognize that the aerial vehicle 210 or the dataprocessing system 270 may communicate with any of a number of computingdevices that are capable of communicating over the network 280,including but not limited to set-top boxes, personal digital assistants,digital media players, web pads, laptop computers, desktop computers,electronic book readers, and the like. The protocols and components forproviding communication between such devices are well known to thoseskilled in the art of computer communications and need not be describedin more detail herein.

The data and/or computer executable instructions, programs, firmware,software and the like (also referred to herein as “computer executable”components) described herein may be stored on a computer-readable mediumthat is within or accessible by computers or computer components such asthe processor 212 or the processor 274, or any other computers orcontrol systems utilized by the aerial vehicle 210 or the dataprocessing system 270, and having sequences of instructions which, whenexecuted by a processor (e.g., a central processing unit, or “CPU”),cause the processor to perform all or a portion of the functions,services and/or methods described herein. Such computer executableinstructions, programs, software, and the like may be loaded into thememory of one or more computers using a drive mechanism associated withthe computer readable medium, such as a floppy drive, CD-ROM drive,DVD-ROM drive, network interface, or the like, or via externalconnections.

Some embodiments of the systems and methods of the present disclosuremay also be provided as a computer-executable program product includinga non-transitory machine-readable storage medium having stored thereoninstructions (in compressed or uncompressed form) that may be used toprogram a computer (or other electronic device) to perform processes ormethods described herein. The machine-readable storage media of thepresent disclosure may include, but is not limited to, hard drives,floppy diskettes, optical disks, CD-ROMs, DVDs, ROMs, RAMs, erasableprogrammable ROMs (“EPROM”), electrically erasable programmable ROMs(“EEPROM”), flash memory, magnetic or optical cards, solid-state memorydevices, or other types of media/machine-readable medium that may besuitable for storing electronic instructions. Further, embodiments mayalso be provided as a computer executable program product that includesa transitory machine-readable signal (in compressed or uncompressedform). Examples of machine-readable signals, whether modulated using acarrier or not, may include, but are not limited to, signals that acomputer system or machine hosting or running a computer program can beconfigured to access, or including signals that may be downloadedthrough the Internet or other networks.

As is discussed above, propellers having reconfigurable blade tips maybe placed into different geometric configurations corresponding todifferent modes of operation of an aerial vehicle, or for any otherpurpose. For example, in some embodiments, a propeller may align one ormore blade tips at a first cant angle with respect to a blade rootduring a take-off operation, at a second cant angle with respect to theblade root during a transit or in forward flight, or at a third cantangle with respect to the blade root when during a landing operation.Referring to FIG. 3, a flow chart 300 of one process for one process foroperating an aerial vehicle having a propeller with a geometricallyreconfigurable blade in accordance with embodiments of the presentdisclosure is shown. At box 310, operation of an aerial vehicle having apropeller in an initial geometric configuration is commenced. Thegeometric configuration may be specifically selected for an intendedevolution or mission of the aerial vehicle, e.g., a take-off or landingevent. For example, an aerial vehicle having a propeller withreconfigurable blade tips may depart from an origin with the blade tipsat zero degree (0°) cant angles with respect to axes defined by thepropeller's blade roots. At box 320, operation of the aerial vehicle ismonitored, e.g., using one or more sensors or control systems, includingbut not limited to one or more of the environmental or operationalsensors 220 described above with regard to FIG. 2, or any other sensorsor sensing systems.

At box 330, whether a control signal requesting a change in thegeometric configuration is received may be determined. The controlsignal may be received from a control system having one or moreprocessors, and may be provided on a predetermined schedule or at apredetermined time, or in response to one or more sensed operatingcharacteristics or environmental conditions. For example, a transit plancomprising information regarding a mission to be performed by the aerialvehicle, including but not limited to dates or times at which the aerialvehicle is to depart from or arrive at an origin, a destination, or oneor more intervening waypoints, or actions or evolutions to be performedby the aerial vehicle at the origin, at the destination, or at thewaypoints, or while in transit, may further include informationregarding geometric configurations of propeller blades (e.g., cantangles at which blade tips should be aligned with respect to bladeroots) during one or more aspects of the transit, the actions or theevolutions.

If the control signal is received, then the process advances to box 340,where at least one attribute of one or more of the blades of thepropeller is modified in response to the control signal. For example,where the propeller is equipped with reconfigurable blade tips, a cantangle of one or more of the blade tips with respect to a correspondingone of the blade roots may be modified accordingly. At box 350, whetherthe continued operation of the aerial vehicle with the propeller in thecurrent geometric configuration is desired may be determined. If thecontinued operation of the aerial vehicle in the current geometricconfiguration is desired, then the process returns to box 320, where theoperation of the aerial vehicle is monitored, e.g., using one or moresensors or sensing systems. If the continued operation of the aerialvehicle in the current geometric configuration is no longer desired,however, then the process ends.

Accordingly, the systems and methods of the present disclosure may beutilized to change a geometric configuration of one or more blades ofone or more propellers, e.g., in accordance with an operational mode ofan aerial vehicle, or in response to one or more operatingcharacteristics of the aerial vehicle (e.g., altitudes, courses, speeds,rates of climb or descent, turn rates, accelerations, tracked positions,fuel level, battery level or radiated noise) or environmental conditionsin a vicinity of the aerial vehicle (e.g., temperatures, pressures,humidities, wind speeds, wind directions, times of day or days of aweek, month or year when an aerial vehicle is operating, measures ofcloud coverage, sunshine, or surface conditions or textures), or for anyother reason.

As is discussed above, a geometric configuration of a propeller blademay be changed in any manner, e.g., from a first configuration to asecond configuration, while the propeller blade is rotating inaccordance with the present disclosure. Referring to FIGS. 4A, 4B, and4C, views of reconfigurable propellers 420A, 420B, and 420C inaccordance with embodiments of the present disclosure are shown. Exceptwhere otherwise noted, reference numerals preceded by the number “4”shown in FIG. 4A, 4B or 4C indicate components or features that aresimilar to components or features having reference numerals preceded bythe number “1” shown in FIGS. 1A through 1C.

As is shown in FIG. 4A, a first propeller 420A includes fourreconfigurable propeller blades 430A mounted about a hub 450A. Each ofthe reconfigurable blades 430A includes an adjustable blade tip 432Amounted to a blade root 435A at cant angles that may be modified duringoperation. At a first time t₁, the blade tips 432A are eachsubstantially co-aligned with axes defined by the blade roots 435A,e.g., at zero degree (0°) cant angles with respect to such roots 435A.At a second time t₂, however, the blade tips 432A are each alignedsubstantially perpendicular to the axes defined by the blade roots 435A,e.g., at ninety degree (90°) cant angles with respect to such roots435A.

As is shown in FIG. 4B, a second propeller 420B includes a pair ofreconfigurable propeller blades 430B mounted about a hub 450B. Each ofthe reconfigurable blades 430B includes an adjustable blade trailingedge 432B mounted to a blade root 435B at cant angles that may bemodified during operation. At a first time t₁, the blade trailing edges432B are each substantially co-aligned with the blade roots 435B, e.g.,within a common plane with such roots 435B. At a second time t₂,however, the blade trailing edges 432B are each aligned substantiallyperpendicular to planes of the blade roots 435B, e.g., at ninety-degree(90°) cant angles with respect to such roots 435B.

As is shown in FIG. 4C, a third propeller 420C includes threereconfigurable propeller blades 430C mounted about a hub 450C. Each ofthe reconfigurable blades 430C includes an adjustable camber 432C of ablade root 435C at widths that may be modified during operation. At afirst time t₁, the blade cambers 432C are fully extended to a maximumwidth of the blade roots 435C. At a second time t₂, however, the bladecambers 432C are fully retracted within the blade roots 435C to aminimum width.

As is also discussed above, the geometric configurations of propellerblades (e.g., cant angles of blade tips with respect to blade roots) maybe changed on a regular or irregular basis while in operation. Forexample, the geometric configurations may be automatically changed toreduce an area of a blade presented during forward flight, and also tomitigate the adverse effects of tip vortices, by minimizing a cant angleof a blade tip with respect to a blade root when the blade is aligned ina longitudinal orientation (e.g., pointed in a direction of the forwardflight, or in an opposite direction) and maximizing the cant angle ofthe blade tip when the blade is aligned in a transverse direction (e.g.,perpendicular to the direction of the forward flight). Referring to FIG.5, a flow chart 500 of one process for one process for operating anaerial vehicle having a propeller with a geometrically reconfigurableblade in accordance with embodiments of the present disclosure is shown.At box 510, operation of an aerial vehicle with a reconfigurablepropeller in a static geometric configuration, e.g., with a blade tip ata fixed cant angle with respect to a blade root, is commenced. At box520, operation of the aerial vehicle is monitored, e.g., using one ormore sensors or control systems.

At box 530, whether a control signal requesting a change in thegeometric configuration is received, e.g., using one or more sensors orcontrol systems, may be determined. If the control signal is received,then the process advances to box 540, where at least one attribute ofone or more of the blades of the propeller is cyclically modified inaccordance with a predetermined schedule defined by a dynamic geometricconfiguration, e.g., in response to the control signal. For example,with regard to an angular orientation of the propeller, a cant angle ofone or more blade tips of the propeller with respect to a blade root maybe continuously changed, e.g., between a predefined range of cantangles, as the propeller rotates in operation. Alternatively, in someother embodiments, the cant angles of the blade tips may be changed onan iterative basis, at various fixed angular intervals. In still otherembodiments, the cant angles of the blade tips may be changed on anirregular basis.

At box 550, whether the continued operation of the aerial vehicle withthe propeller in the current dynamic geometric configuration is desiredmay be determined. If the continued operation of the aerial vehicle inthe current geometric configuration is desired, then the process returnsto box 520, where the operation of the aerial vehicle is monitored,e.g., using one or more sensors or sensing systems. If the continuedoperation of the aerial vehicle in the current dynamic geometricconfiguration is no longer desired, however, then the process ends.

As is discussed above, a geometric configuration of a propeller blademay be changed on a regular basis, e.g., consistent with an angularorientation of the propeller blade, while the propeller is rotating. Forexample, in some embodiments, a cant angle of a blade tip of a propellerblade with respect to a blade root may be changed with respect to anangular orientation of the propeller blade during operation. Referringto FIG. 6, a view of aspects of one aerial vehicle having a propellerwith a geometrically reconfigurable blade in accordance with embodimentsof the present disclosure is shown. Except where otherwise noted,reference numerals preceded by the number “6” shown in FIG. 6 indicatecomponents or features that are similar to components or features havingreference numerals preceded by the number “4” shown in FIG. 4A, 4B or4C, or by the number “1” shown in FIGS. 1A through 1C.

As is shown in FIG. 6, an aerial vehicle 610 includes a plurality ofreconfigurable propellers 620, each of which is mounted to a rotatablemotor 660. Each of the propellers 620 includes a pair of blades 630, 640mounted about a hub 650. The blade 630 includes a reconfigurable bladetip 632 mounted to a blade root 635. The blade 640 includes areconfigurable blade tip 642 mounted to a blade root 645.

In accordance with the present disclosure, a propeller configuration maybe changed on a regular basis, e.g., in a manner consistent with therotation of the propeller. For example, as is shown in FIG. 6, when thepropellers 620 are aligned parallel to a direction of travel of theaerial vehicle 610, e.g., at zero degree (0°) or one hundred eightydegree (180°) angles about their axes of rotation, the blade tips 632,642 are fully extended and co-aligned with the blade roots 635, 645.When the propellers 620 are rotated perpendicular to the direction oftravel of the aerial vehicle 610, e.g., at ninety degree (90°) or twohundred seventy degree (270°) angles about their axes of rotation, theblade tips 632, 642 are fully raised with respect to the blade roots635, 645. Thus, the geometries of the respective blades 630, 640 may bechanged to resist the effects of tip vortices when the blades 630, 640are perpendicular to the direction of travel of the aerial vehicle 610,and to reduce sizes of profiles presented by such tips and any draginduced thereby when the blades 630, 640 are aligned with the directionof travel of the aerial vehicle 610.

As is further discussed above, a geometric configuration of a propellerblade may be changed in response to a sensed operating characteristic orenvironmental condition of an aerial vehicle. For example, a geometricconfiguration of a propeller blade may be automatically modified whenthe aerial vehicle arrives at a given location, reaches a predeterminedaltitude or speed, experiences a specific rate of climb or descent, orrate of turn), or enters within a predefined range of a particularstructure, property individual or location of interest. The geometricconfiguration of the propeller blade may be further modified when theaerial vehicle senses or a specific temperature, barometric pressure,humidity level, wind speed or ambient sound level, or predicts that sucha temperature, pressure, humidity level, wind speed, or ambient soundlevel may soon be encountered. The geometric configuration of thepropeller blade may be further modified when the aerial vehicledetermines that a weather event is anticipated, is occurring, or hasoccurred. The geometric configuration of the propeller blade may also bemodified when the aerial vehicle is determined to be radiating sound ata predetermined sound pressure level (or intensity) or frequency, orwhen such a sound is otherwise sensed or detected.

Referring to FIG. 7, a flow chart 700 of one process for one process foroperating an aerial vehicle having a propeller with a geometricallyreconfigurable blade in accordance with embodiments of the presentdisclosure is shown. At box 710, operation of an aerial vehicle with areconfigurable propeller in an initial geometric configuration iscommenced, and at box 720, the operation of the aerial vehicle ismonitored, e.g., using one or more sensors or control systems.

At box 730, an environmental condition or operational characteristic ofthe aerial vehicle is sensed by one or more sensors. For example, theenvironmental condition may be any determinable factor or metricassociated with an area in which the aerial vehicle is operating, or isexpected to operate, including but not limited to information or dataregarding atmospheric or weather conditions, ground conditions at anorigin or a destination or along a predetermined route, or any otherrelevant factor. Likewise, the operational characteristic may be anydeterminable factor or metric associated with the operation of theaerial vehicle, including but not limited to altitudes, positions,velocities, accelerations, or rates of climb, turn or descent, as wellas radiated sound levels or rotational speeds (e.g., angular velocities)of one or more engines or motors. The aerial vehicle may be configuredto monitor one or more environmental conditions or operationalcharacteristics on a continuous basis, or at predetermined times or inaccordance with a predetermined schedule. Alternatively, those ofordinary skill in the pertinent art will recognize that the processrepresented in the flow chart 700 of FIG. 7 may operate based on aprediction of an environmental condition or operational characteristic,which may be determined according to one or more machine learningsystems or algorithms, which may generate one or more models forpredicting such conditions or characteristics based on substantiallylarge corpuses of historical data regarding prior operations of one ormore aerial vehicles, including but not limited to environmentalconditions or operational characteristics encountered by such vehicles.

At box 740, whether the sensed environmental condition and/or the sensedoperational characteristic corresponds to a predetermined threshold isdetermined. For example, a sensed position, temperature, wind speed ordirection, or radiated sound level (or, alternatively, a predictedposition, temperature, wind speed or direction, or radiated sound level)may be compared to a threshold position, temperature, wind speed ordirection, or radiated sound level. If the sensed environmentalcondition and/or the sensed operational characteristic does notcorrespond to the predetermined limit, then the process returns to box720, where the operation of the aerial vehicle is monitored accordingly.

If the sensed environmental condition and/or the sensed operationalcharacteristic corresponds to the predetermined limit, however, then theprocess advances to box 750, where the geometric configuration of thepropeller is changed based on the sensed environmental condition and/orthe sensed operational characteristic. For example, the geometricconfiguration of the propeller may be changed by a predetermined extent,e.g., a blade tip may be automatically placed at a predetermined cantangle with respect to a blade root, when the sensed environmentalcondition and/or the sensed operational characteristic is determined tocorrespond to the predetermined limit. Alternatively, the extent towhich the geometric configuration is changed may be determined based atleast in part on the sensed environmental condition and/or the sensedoperational characteristic. For example, where it is determined thatnoise at a first sound pressure level is radiating from an aerialvehicle, a blade tip may be repositioned to a first cant angle withrespect to an axis of extension, e.g., in a radial direction, defined bya blade root. Where it is determined that noise at a second soundpressure level is radiating from the aerial vehicle, however, the bladetip may be repositioned to a second cant angle with respect to the axisof extension.

At box 760, whether the continued operation of the aerial vehicle withthe propeller in the current geometric configuration is desired may bedetermined. If the continued operation of the aerial vehicle in thecurrent geometric configuration is desired, then the process returns tobox 720, where the operation of the aerial vehicle is monitored, e.g.,using one or more sensors or sensing systems. If the continued operationof the aerial vehicle in the current geometric configuration is nolonger desired, however, then the process ends.

Referring to FIG. 8, a view of aspects of one aerial vehicle 810 havinga propeller with a geometrically reconfigurable blade in accordance withembodiments of the present disclosure is shown. Except where otherwisenoted, reference numerals preceded by the number “8” shown in FIG. 8indicate components or features that are similar to components orfeatures having reference numerals preceded by the number “6” shown inFIG. 6, by the number “4” shown in FIG. 4A, 4B or 4C, or by the number“1” shown in FIGS. 1A through 1C.

As is shown in FIG. 8, the multi-rotor aerial vehicle 810 is en routefrom an origin in Boston, Mass., to a destination in New York, N.Y., byway of Storrs, Conn. The aerial vehicle 810 includes at least onereconfigurable propeller 820 having a pair of blades 830, 840 mountedabout a hub 850. The blade 830 includes a reconfigurable blade tip 832joined to a blade root 835. The blade tip 832 may be realigned to anycant angle θ₁ with respect to the blade root 835, e.g., by one or moremechanical or electrical means. Likewise, the blade 840 includes areconfigurable blade tip 842 joined to a blade root 845. The blade tip842 may be realigned to any cant angle θ₂ with respect to the blade root845. The cant angles θ₁, θ₂ at which the blade tips 832, 842 areprovided with respect to the blade roots 835, 845 may be selected on anybasis, in order to balance operational commitments of the aerial vehicle810 against the adverse effects of tip vortices on the propeller 820, orfor any other purpose.

As is discussed above, in accordance with the present disclosure, apropeller may be geometrically reconfigured in any manner and inresponse to any environmental conditions or operational characteristics.For example, the propellers of the present disclosure may bereconfigured based on a mode of transit of the aerial vehicle (e.g.,vertical evolutions such as take-offs, landings or altitude changes, orhorizontal evolutions such as transits between the origin and thedestination, or any intervening waypoints. The propellers may bereconfigured on any basis during the operation of the aerial vehicle,including but not limited to dynamic operational characteristics such asaltitudes, courses, speeds, rates of climb or descent, turn rates,accelerations, tracked positions, fuel level, battery level or radiatednoise; or environmental conditions such as temperatures, pressures,humidities, wind speeds, wind directions, times of day or days of aweek, month or year when an aerial vehicle is operating, measures ofcloud coverage or sunshine, or surface conditions or textures.

As is shown in FIG. 8, the aerial vehicle 810 begins its transit bydeparting from the origin with cant angles of the blade tips 832, 842provided at ninety degrees (90°), viz., one or both of the cant angle θ₁or the cant angle θ₂, with respect to the blade roots 835, 845, in orderto optimize the efficiency of the propeller 820 during the verticalflight operations.

Once the aerial vehicle 810 reaches a cruising altitude, the blade tips832, 842 may transition to an optimal configuration for a transit fromthe origin to an intervening waypoint, based on any operationalcharacteristics or environmental conditions such as weather, wind,duration, distance, available power, radiated noise, surface conditions,legal or regulatory restrictions, or any other relevant factors, thatmay be predicted or sensed while the aerial vehicle 810 is en route. Forexample, as is shown in FIG. 8, when the aerial vehicle 810 is travelingfrom the origin to the waypoint in favorable conditions such as clearskies, warm temperatures and mild winds, the aerial vehicle 810 mayoperate the propeller 820 with the blade tips 832, 842 at static zerodegree (0°) cant angles with respect to the blade roots 835, 845 inorder to minimize drag during the transit. Alternatively, as isdiscussed above, the blade tips 832, 842 may be reconfigured in adynamic manner during the transit, e.g., with the blade tips 832, 842co-aligned with the blade roots 835, 845 when the propeller 820 isaligned with a direction of travel of the aerial vehicle 810, and withthe blade tips 832, 842 at a positive cant angle with respect to theblade roots 835, 845 when the propeller 820 is aligned perpendicular tothe direction of travel. Those of ordinary skill in the pertinent artswill recognize that the blade tips or other features of a reconfigurablepropeller may be geometrically reconfigured in any static or dynamicmanner in accordance with the present disclosure.

When the aerial vehicle 810 reaches the waypoint, the cant angles of theblade tips 832, 842 may be further modified with respect to the bladeroots 835, 845 in a manner consistent with any requirements of theaerial vehicle 810, e.g., missions or functions being performed by theaerial vehicle 810. For example, as is shown in FIG. 8, when the aerialvehicle 810 is performing a specific mission, such as the retrieval ordelivery of one or more payloads, the aerial vehicle 810 may operate thepropeller with the blade tips 832, 842 at an cant angle with respect tothe blade roots 835, 845, viz., a sixty degree (60°) cant angle, may beselected based on any relevant factor, including surface conditions,population density, air traffic, wind speed, weather conditions or otherfactors relating to the mission or the waypoint.

Subsequently, when the aerial vehicle 810 departs from the waypoint, theblade tips may transition to an optimal configuration for a transit fromthe waypoint to the destination, based on any operationalcharacteristics or environmental conditions that may be predicted orsensed while the aerial vehicle 810 is en route. For example, as isshown in FIG. 8, when the aerial vehicle 810 is traveling in unfavorableor uncertain conditions such as cloudy skies or amid rain showers, or incolder weather or higher winds, the aerial vehicle 810 may operate theblade tips 832, 842 at static forty-five degree (45°) cant angles withrespect to the blade roots 835, 845 in order to reduce any adverseeffects of tip vortices while maintaining proper control over the aerialvehicle 810 during such conditions. Alternatively, as is discussedabove, the blade tips 832, 842 may be reconfigured in a dynamic mannerduring the transit.

Finally, as the aerial vehicle 810 arrives at the destination, the bladetips 832, 842 may again be reconfigured with respect to the blade roots835, 845 as the aerial vehicle 810 conducts a landing operation at thedestination. As is shown in FIG. 8, the blade tips 832, 842 may berepositioned to ninety-degree (90°) cant angles with respect to theblade roots 835, 845 in order to optimize the efficiency of thepropeller 820 during the vertical flight operations.

Those of ordinary skill in the pertinent arts will recognize that thepropellers disclosed herein may be reconfigured in accordance with aschedule, which may be established in accordance with a transit plan foran aerial vehicle, such that the propellers are geometricallyreconfigured when the aerial vehicle reaches a predetermined position,altitude or speed, or at a predetermined time. The propellers may alsobe reconfigured when one or information or data regarding one or moreoperational characteristics or environmental conditions of the aerialvehicle is sensed or predicted, and the aerial vehicle may include oneor more sensors for continuously monitoring for such characteristics orconditions, or one or more computer processors for predicting suchcharacteristics or conditions, e.g., according to one or more machinelearning systems or algorithms. For example, the propellers may bereconfigured when a specific radiated noise level, battery capacity,weather condition, or motor speed (e.g., angular velocity) is recognizedor anticipated. The reconfigurations of the propellers may be static ordynamic in nature, and may be made to any degree or extent betweenmaximum and minimum physical or functional limits. For example, a bladetip may be reconfigured to any cant angle with respect to a blade rootbetween a maximum absolute limit and zero (e.g., when the blade tip isco-aligned with an axis of radial extension defined by the blade root).

Although the disclosure has been described herein using exemplarytechniques, components, and/or processes for implementing the systemsand methods of the present disclosure, it should be understood by thoseskilled in the art that other techniques, components, and/or processesor other combinations and sequences of the techniques, components,and/or processes described herein may be used or performed that achievethe same function(s) and/or result(s) described herein and which areincluded within the scope of the present disclosure.

For example, those of ordinary skill in the pertinent arts willrecognize that uses of one or more of the reconfigurable propellersdisclosed herein are not so limited, and may be utilized in connectionwith any type or form of aerial vehicle (e.g., manned or unmanned).Reconfigurable propellers of the present disclosure may have any numberof blades, and any portion of such blades may be reconfigured in anymanner during operations of an aerial vehicle. Likewise, a determinationthat a reconfigurable propeller should be geometrically reconfigured maybe made on any basis. The manner in which a configuration of a propellermay be determined is not limited by any of the embodiments of thepresent disclosure.

It should be understood that, unless otherwise explicitly or implicitlyindicated herein, any of the features, characteristics, alternatives ormodifications described regarding a particular embodiment herein mayalso be applied, used, or incorporated with any other embodimentdescribed herein, and that the drawings and detailed description of thepresent disclosure are intended to cover all modifications, equivalentsand alternatives to the various embodiments as defined by the appendedclaims. Moreover, with respect to the one or more methods or processesof the present disclosure described herein, including but not limited tothe processes represented in the flow charts of FIGS. 3, 5 and 7, ordersin which such methods or processes are presented are not intended to beconstrued as any limitation on the claimed inventions, and any number ofthe method or process steps or boxes described herein can be combined inany order and/or in parallel to implement the methods or processesdescribed herein. Also, the drawings herein are not drawn to scale.

Conditional language, such as, among others, “can,” “could,” “might,” or“may,” unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey in apermissive manner that certain embodiments could include, or have thepotential to include, but do not mandate or require, certain features,elements and/or steps. In a similar manner, terms such as “include,”“including” and “includes” are generally intended to mean “including,but not limited to.” Thus, such conditional language is not generallyintended to imply that features, elements and/or steps are in any wayrequired for one or more embodiments or that one or more embodimentsnecessarily include logic for deciding, with or without user input orprompting, whether these features, elements and/or steps are included orare to be performed in any particular embodiment.

Disjunctive language such as the phrase “at least one of X, Y, or Z,” or“at least one of X, Y and Z,” unless specifically stated otherwise, isotherwise understood with the context as used in general to present thatan item, term, etc., may be either X, Y, or Z, or any combinationthereof (e.g., X, Y, and/or Z). Thus, such disjunctive language is notgenerally intended to, and should not, imply that certain embodimentsrequire at least one of X, at least one of Y, or at least one of Z toeach be present.

Unless otherwise explicitly stated, articles such as “a” or “an” shouldgenerally be interpreted to include one or more described items.Accordingly, phrases such as “a device configured to” are intended toinclude one or more recited devices. Such one or more recited devicescan also be collectively configured to carry out the stated recitations.For example, “a processor configured to carry out recitations A, B andC” can include a first processor configured to carry out recitation Aworking in conjunction with a second processor configured to carry outrecitations B and C.

Language of degree used herein, such as the terms “about,”“approximately,” “generally,” “nearly” or “substantially” as usedherein, represent a value, amount, or characteristic close to the statedvalue, amount, or characteristic that still performs a desired functionor achieves a desired result. For example, the terms “about,”“approximately,” “generally,” “nearly” or “substantially” may refer toan amount that is within less than 10% of, within less than 5% of,within less than 1% of, within less than 0.1% of, and within less than0.01% of the stated amount.

Although the invention has been described and illustrated with respectto illustrative embodiments thereof, the foregoing and various otheradditions and omissions may be made therein and thereto withoutdeparting from the spirit and scope of the present disclosure.

What is claimed is:
 1. An unmanned aerial vehicle comprising: apropeller comprising a first blade, a second blade and a hub, whereinthe first blade comprises a first blade root having a first proximal endcoupled to the hub and a first distal end pivotably joined to a firstblade tip, and wherein the second blade comprises a second blade roothaving a second proximal end coupled to the hub; a motor having a shaftrotatably coupled to the hub, wherein the motor is configured to rotatethe propeller about an axis defined by the shaft; and a control systemcomprising at least one computer processor, wherein the control systemis in communication with at least the motor and the propeller, andwherein the control system is configured to execute a method comprising:causing the motor to rotate the propeller at a selected rotationalspeed; with the motor rotating the propeller at the selected rotationalspeed, aligning the first blade tip at a first cant angle with respectto the first blade root at a first time; aligning the first blade tip ata second cant angle with respect to the first blade root at a secondtime; aligning the first blade tip at the first cant angle at a thirdtime; and aligning the first blade tip at the second cant angle at afourth time.
 2. The unmanned aerial vehicle of claim 1, wherein each ofthe first time, the second time, the third time and the fourth time isin accordance with a first schedule, and wherein the method furthercomprises: programming a control system to pivot the first blade tipabout the first hinge in accordance with the first schedule.
 3. Theunmanned aerial vehicle of claim 2, wherein the first blade root is in afirst angular orientation about the axis defined by the shaft at thefirst time, and wherein the first blade root is not in the first angularorientation about the first axis at the third time.
 4. A methodcomprising: causing a first propeller to rotate about a first axisdefined by a first shaft of a first motor, wherein the first propellercomprises a first blade coupled to a first hub and a second bladecoupled to the first hub, and wherein the first blade comprises a firstblade root having a first proximal end mounted to the first hub and afirst distal end pivotably joined to a first blade tip by a first hinge;and with the first propeller rotating about the first axis, causing thefirst blade tip to be aligned at a first cant angle with respect to thefirst blade root at a first time, wherein the first blade root is in afirst angular orientation about the first axis at the first time;causing the first blade tip to be aligned at a second cant angle withrespect to the first blade root at a second time; and causing the firstblade tip to be aligned at the first cant angle at a third time, whereinthe first blade root is not in the first angular orientation about thefirst axis at the third time.
 5. The method of claim 4, wherein each ofthe first time, the second time and the third time is in accordance witha first schedule, and wherein the method further comprises: programminga control system to pivot the first blade tip about the first hinge inaccordance with the first schedule.
 6. The method of claim 5, furthercomprising: causing the first blade tip to be aligned at the second cantangle at a fourth time, wherein the first time and the third time areseparated by a predetermined period of time according to the firstschedule, and wherein the second time and the fourth time are separatedby the predetermined period of time according to the first schedule. 7.The method of claim 4, wherein the first motor is coupled to a frame ofan aerial vehicle.
 8. The method of claim 7, wherein the aerial vehiclefurther comprises at least one sensor, and wherein the method furthercomprises: prior to the first time, predicting at least one attribute ofthe aerial vehicle at one or more of the first time or the second time;and selecting at least one of the first cant angle, the second cantangle, the first time or the second time based at least in part on thepredicted attribute.
 9. The method of claim 8, further comprising: priorto the first time, defining a model for predicting the at least oneattribute of the aerial vehicle according to at least one machinelearning algorithm by at least one computer processor; providinghistorical data regarding operations of aerial vehicles to the model asinputs by the at least one computer processor; receiving at least oneoutput from the model; and predicting the at least one attribute of theaerial vehicle at the one or more of the first time or the second timebased at least in part on the at least one output.
 10. The method ofclaim 7, wherein the aerial vehicle further comprises at least onesensor, and wherein the method further comprises: after the second time,capturing information by the at least one sensor; determining anattribute of the aerial vehicle based at least in part on theinformation captured by the at least one sensor prior to the first time;selecting at least one of a third cant angle, a fourth cant angle, athird time or a fourth time based at least in part on the attribute ofthe aerial vehicle; and programming the control system to pivot thefirst blade tip about the first hinge in accordance with a secondschedule, wherein the second schedule comprises: causing the first bladetip to be aligned at the third cant angle with respect to the firstblade root at the third time; and causing the first blade tip to bealigned at the fourth cant angle with respect to the first blade root atthe fourth time.
 11. The method of claim 7, further comprising: causinga second propeller to rotate about a second axis defined by a secondshaft of a second motor, wherein the second propeller comprises a thirdblade coupled to a second hub and a fourth blade coupled to the secondhub, wherein the third blade comprises a second blade root having asecond proximal end mounted to the second hub and a second distal endpivotably joined to a second blade tip by a second hinge; and with thesecond propeller rotating about the second axis, causing the secondblade tip to be aligned at a third cant angle with respect to the secondblade root at a third time; and causing the second blade tip to bealigned at a fourth cant angle with respect to the second blade root ata fourth time.
 12. The method of claim 4, wherein the aerial vehiclefurther comprises at least one sensor, and wherein the method furthercomprises: prior to the first time, capturing information by the atleast one sensor; determining an attribute of the aerial vehicle basedat least in part on the information captured by the at least one sensorprior to the first time; and selecting at least one of the first cantangle, the second cant angle, the first time or the second time based atleast in part on the attribute of the aerial vehicle.
 13. The method ofclaim 12, wherein the attribute is at least one of: a position of theaerial vehicle; an altitude of the aerial vehicle; a speed of the aerialvehicle; an acceleration of the aerial vehicle; a rate of climb of theaerial vehicle; a rate of descent of the aerial vehicle; a turn rate ofthe aerial vehicle; a sound pressure level or a frequency of a noiseradiated from the aerial vehicle; an angular velocity of the firstmotor; an atmospheric temperature in a vicinity of the aerial vehicle; abarometric pressure in the vicinity of the aerial vehicle; a weatherevent in the vicinity of the aerial vehicle; a level of cloud coveragein the vicinity of the aerial vehicle; a level of sunshine in thevicinity of the aerial vehicle; and a surface condition in the vicinityof the aerial vehicle.
 14. The method of claim 4, wherein the secondblade comprises a second blade root having a second proximal end mountedto the first hub and a second distal end pivotably joined to a secondblade tip by a second hinge, and wherein the method further comprises:with the first propeller rotating about the first axis, causing thesecond blade tip to be aligned at a third cant angle with respect to thesecond blade root at a third time; and causing the second blade tip tobe aligned at a fourth cant angle with respect to the second blade rootat a fourth time.
 15. The method of claim 4, wherein the first propellerfurther comprises a first operator disposed at least in part within thefirst blade root, wherein the first blade tip is caused to be aligned atthe first cant angle with respect to the first blade root at the firsttime by the first operator, and wherein the first blade tip is caused tobe aligned at the second cant angle with respect to the first blade rootat the second time by the first operator.
 16. A propulsion systemcomprising: a propeller comprising a first blade, a second blade and ahub, wherein the first blade comprises a first blade root having a firstproximal end mounted to the hub and a first distal end pivotably joinedto a first blade tip by a first hinge, and wherein the second bladecomprises a second blade root having a second proximal end mounted tothe hub; a first operator configured to pivot the first blade rootwithin a first cant angle range about an axis defined by the firsthinge, wherein at least a portion of the first operator is disposedwithin the first blade root; a motor, wherein the motor comprises ashaft rotatably coupled to the hub, and wherein the motor is configuredto rotate the propeller about an axis defined by the shaft; and at leastone computer processor in communication with at least the motor and thefirst operator, wherein the at least one computer processor isconfigured to execute a method comprising: causing the motor to rotatethe propeller at a first rotational speed; and with the motor rotatingthe propeller at the first rotational speed, causing the operator topivot the first blade tip from a first cant angle with respect to theaxis defined by the first hinge to a second cant angle with respect tothe axis defined by the first hinge over a first period of time; andcausing the operator to pivot the first blade tip from the second cantangle to the first cant angle over a second period of time, wherein thefirst period of time and the second period of time are in accordancewith a schedule.
 17. The propulsion system of claim 16, wherein themethod further comprises: with the motor rotating the propeller at thefirst rotational speed, causing the operator to pivot the first bladetip from the first cant angle to the second cant angle over a thirdperiod of time, wherein the third period of time is in accordance withthe schedule.
 18. The propulsion system of claim 17, wherein the firstperiod of time begins at a first time and ends at a second time, whereinthe second period of time begins at a third time and ends at a fourthtime, wherein the third period of time begins at a fifth time and endsat a sixth time, wherein the first blade is in a first angularorientation about the axis defined by the shaft at the first time, andwherein the first blade is not in the first angular orientation aboutthe axis defined by the shaft at the fifth time.
 19. The propulsionsystem of claim 16, wherein the second blade root further comprises asecond distal end pivotably joined to a second blade tip by a secondhinge, wherein the propulsion system further comprises a second operatorconfigured to pivot the second blade root within a second cant anglerange about an axis defined by the second hinge, wherein at least aportion of the second operator is disposed within the second blade root,and wherein the method further comprises: with the motor rotating thepropeller at the first rotational speed, causing the operator to pivotthe second blade tip from a third cant angle with respect to the axisdefined by the second hinge to a fourth cant angle with respect to theaxis defined by the second hinge over a third period of time; andcausing the operator to pivot the first blade tip from the fourth cantangle to the third cant angle over a fourth period of time, wherein thethird period of time and the fourth period of time are in accordancewith the schedule.
 20. The propulsion system of claim 16, wherein thefirst cant angle range is between a positive normal cant angle and anegative normal cant angle.